Method of making a refractory hot top panel insert



Nov. 11, 1969 w. M. CHARMAN, JR, ET AL 3,477,493

METHOD OF MAKING A REFRACTORY HOT TOP PANEL INSERT 2 Sheets-Sheet 1Filed May 4, 1967 FIG .1

FIG .4

lNVENTOR S. WALT M. C/IARMAN, JR.

sea/ea: J'M/DDAUGAQ J BY 4 l i E y .4770 5Y9 Nov. 11, 1969 w. JR" ET AL3,477,493

METHOD OF MAKING A REFRACTORY HOT TOP PANEL INSERT Filed May 4, 1967 2Sheets-Sheet 2 FIG .7

INVENTORS. WALTER M. CHARMAA; JR. 60R6 J M/DDAUG/i, JR.

A TTURNEYJ is .then dried to form el insert unit.

United States Patent Ofiice 3,477,493 Patented Nov. 11, 1969 Us. or.164-7 3 Claims ABSTRACT OF THE ISCLOSURE -A refractory panel insert unitto besurrounded by an ingot mold wall or a hot top casing includes aplurality or highly insulating refractory panels which are integrall-yconnected by frangible refractory connecting portions. A wire meshnetting is embedded at least partially in the back of the panels andprovides a hinge interconnection between the panels upon breaking of thefrangible connecting portions. The entire insert unit is manufactured bymaking a slurry of sand, a resin binder, an inorganic fibrous material,and water, and depositing the slurry on a filter'screen in a frame overa vacuum box, and embedding the wirenetting in the layer of slurry.Applying a vacuum under the filter screen in the vacuum box effectsremoval 'of part of the water from the slurry and leaves a wet mat inwhich is embedded wire netting. The wet mat the highly insulatingrefractory pan- The present invention relates to a hot topstructure anda method of making the same, and more particularly to a refractory panelinsert unit having a plurality of interconnected panel sections whichare relatively movable to "form a tubular container at the upper end ofan ingot mold to permitmetal in a molten state to be fed to thesolidfying metal in the ingot mold to compensate for shrinkage of themetal during solidification thereof.

The-present invention relates to a method of making an'insulating panelinsert unit comprised of a plurality of'flat panels interconnected byflexible hinge means so that the panels may be moved from a flatposition to a closed'configuration defining a tubular structure.

I An object of the present invention is to provide a new and improvedmethod for making a highly insulating 'u'nitof the type described inwhich the hinge means is embedded in frangible portions extendingbetween adja cent panels and folded integrally. with the panels. 7,

"A still further object of the present invention is "to provide a newand improved method for making a highly insulating panel insert unit ofthe kind described, and

which includes the steps of placing the flexible hinge backing,preferably a flexible wire netting or screen on, the Qfilter. screen ofa vacuum box, placing a contoured mold- -ing frame shaped so as to formthe refractory panels and panel 'connecting portions over the flexiblewire netting and on. thefilterscreen, pouring a refractory slurry intothe contoured molding frame, and partially vacuum dewatering therefractory slurry to form or mold a wet refractory mat, removing thecontour molding frame from the wet matpanels, and drying the wetness outof the "mat by oven baking or other means to form the highly insulatingpanel insert unit. V

Another objectof the present invention is to provide beneath the filterscreen to remove most of the liquid from the slurry after the slurry ispoured into the mold and flows beneath the bars and around the wirenetting to provide the frangible portions integrally interconnecting theadjacent panels.

.The present invention further resides in various novel constructionsand arrangement of parts, and further objects and advantages of thepresent invention will be apparent to those skilled in the art to whichit relates and from the following detailed description of theillustrated embodiment thereof made with reference to the accompanyingdrawings forming a part of this specification and in which similarreference numerals are employed to designate corresponding partsthroughout the several views, and in which:

FIG. 1 is a fragmentary view, partly in elevation and partly in section,of a hot top embodying the present invention and taken approximatelyalong line 1-1 of FIG. 2 and shown mounted in the open upper end of aningot mold;

FIG. 2 is a fragmentary sectional view taken approximately along line2-2 of FIG. 1;

FIG. 3 is a view of a panel insert unit embodying the present inventionand illustrates the insert unit in its unfolded condition;

- FIG. 4 is an enlarged fragmentary transverse sectional view of thepanel insert unit shown in FIG. 3;

, FIG. 5 is a fragmentary vertical sectional view showing an insert unitof the present invention positioned in the open upper end of an ingotmold;

FIG. 6 is a fragmentary and somewhat schematic top plan view of anapparatus for use in making the panel insert unit shown in FIG. 3; and

FIG. 7 is an enlarged fragmentary longitudinal crosssectional view ofthe apparatus shown in FIG. 6.

The present invention provides a novel panel insert unit and method ofmaking the same, and more particularly provides a novel preformed pane].insert unit 10 having .a plurality of integrally connected panels orpanel sections 10a, 1% which are relatively movable to provide amultisided tubular container at the upper end of an ingot mold to hold amass of metal in a molten state above the ingot mold to compensate forshrinkage of the metal in the mold during solidification thereof.Although the preformed panel insert unit 10 can be embodied in or issusceptible for use, with various types of hot top constructions, it isparticularly useful when folded and inserted in a hot top casing, toform a highly insulating hot top A. e

The hot top A is adapted to be mounted in the open upper end of an ingotmold 12 and insofar as the metal casing 11 and its manner of use areconcerned, is conventional. As best shown in FIG. 1, the metal casing 11is of a one-piece construction having a central opening 13, although thecasing can be made in two pieces and fastened together. The opening orinternal cavity 13 is tapered so as to be larger at the bottom than atthe top thereof. It will, of course, be understood that the opening 13could be non-tapered and be of any suitable configuration, such as roundor oval, if desired.

The panel insert unit 10 is adapted to be folded to form a multisidedtubular container or inner hot top lining having sides shapedcomplementary to and corresponding in number to the sides defining theopening 13 in the metal casing 11. In the illustrated embodiment,

" the opening 13 in the metal casing has eight sides and the inner hottop lining is adapted to be inserted into the opening 13 of the metalcasing 11. The panel insert unit is held against the interior sides ofthe casing 11 by the taper of the insert against the taper of thecasing, and is supported by the bottom ring. Clamps might be used onlyin multipiece panel inserts for slabs.

After the panel insert unit 10 is positioned in the metal casing 11, arefractory bottom ring 16 is placed on the lower end of the hot top, andin a manner and for reasons well known to those skilled in the art. Therefractory bottom ring 16 has a recess 17 adjacent its inner peripheryto provide an upwardly facing shoulder that engages the lower edge ofthe panel insert unit 10 to aid in supporting the latter within themetal casing 11 and to prevent molten steel getting behind the panelinsert. However, rings 16 of other configurations with or without recess17 may be used. A wiper strip 18 is positioned on the bottom ring 16 andwhich is engageable with the sides defining the opening at the upper endof the mold'12 for reasons well known to those skilled in the art. Therefractory bottom ring 16 and the wiper strip 18 are adapted to besecured to the casing 11 in any suitable or conventional manner, such asby clips (not shown).

When the hot top A thus equipped is used for a pouring operation, it ispositioned a predetermined distance in the upper open end of an ingotmold 12 and initially held in such position by suitable blocks (notshown). After the pouring of the molten metal into the mold 12 and thehot top A, the blocks are knocked out or destroyed and thereafter thehot top rest-s or floats on the solidifying ingot. The hot top containsa molten mass of metal some of which is fed to the ingot in the mold tocompensate for shrinkage of the metal during the solidifieation.

The panels or panel sections 10a, 10b of the panel insert unit 10 arepreferably made from a highly insulating refractory material and aredisposed in a side-by-side relationship, and with the adjacent panelsbeing integrally connected by refractory portions 22 of reducedthickness as compared to the thickness of the panels 10a, 10b proper.The panels are preferably /3" to 1 /2" in thickness. The panels havesubstantially planar front and back faces 23, 24 which respectively areadapted to face toward and away from the interior of the hollow innerhot top lining when the unit is folded. The panels 10a, 10b, as viewedin FIG. 3, have planar top and bottom edge surfaces 27, 28 joining andextending transversely of the front and back faces 23, 24 and planaradjacent side edge surfaces 30, 31 joining the front face and extendingtoward the back face, but terminating at a location spaced from the backface 24. The top and bottom edge surfaces 27, 28 are preferably taperedso as to form with the front face 23 an obtuse included angletherebetween.

The adjacent side edge surfaces 30, 31 of adjacent panels 10a, 10b arespaced from and face one another and are tapered so as to form with thefront faces 23 an obtuse included angle therebetween. The adjacent sideedge surfaces 30, 31 are planar and tapered toward each other so as tojoin one another at a location intermediate the front and back faces 23,24 of the panels so as to define grooves 32 whose bottoms 33 are spacedfrom the back face 24 of the panels preferably approximately from theback face of the panels. The grooves 32 are V-shaped and the adjacentside edge surfaces 30, 31 define an included angle therebetween. Theangle of the groove will vary depending upon the number of panels in theinsert unit and the angular distance through which the panels must moveto conform to the opening in which they are to be inserted. For example,if four panels are in the insert unit and the unit is to form a completelining, the angle of the groove would be approximately 90 degrees. inthe illustrated embodiment, the angle is approximately 45 degrees.

The refractory portions 22 integrally connecting the adjacent panels10a, 10b extend between the bottoms 33 of the grooves 32 and the backface 24 of the panels. These portions 22 are frangible and breaksubstantially along the bottom 33 of the V-shaped grooves 32 when thepanels 10a, 10b are relatively moved to form the hollow lining, as willbe hereinafter more fully apparent.

The panels 10a, 10b of the preformed insert unit 10 are also hingedlyconected together by a flexible backing or hinge means 40 securedthereto and preferably substantially embedded therein, The hinge means-40 could be of any suitable construction and formed from any suitablematerial which has sufficient strength to suport the respective panelswhen the frangible portions 22 are broken. Preferably, the hinge meansis a flexible wire netting or screen. The flexible wire netting orscreen is preferably completely embedded within the material at alocation spaced rearwardly from the bottom 33 of the grooves 32, andintermediate the bottom 33 of the grooves 32 and the back face 24 of thepanels 10a,10b. The thickness of the wires forming the wire screen issomewhat exaggerated in the drawings for illustrative purposes.

The materials and the compositions from which the panels are made mayvary within certain limits, but where the highly insulating insert unitis to be used against a cast iron casing or in an ingot mold, as shownin the drawings, the insert unit is preferably made of a material whichincludes a granular refractory filler, such as silica flour of suchparticle size as to substantially all be through 200 mesh U.S. sieve, aheat-destructible binder, and an inorganic fibrous material. Theinorganic fibrous material isan asbestos material. A material of thistype is disclosed in application Ser. No. 401,944, filed Oct. 6, 1964and assigned to the same assignee as the present invention. The finepore structure created in the manufacture of the panels make the panelshighly insulating. The high insulating property of the panels can beexpressed by the thermal conductivity or K factor of the material. The Kfactor is, as is well known in the art, the amount of heat in B.t.u.swhich will flow through a 1" thick l-sq, ft. area in one hour per degreeF. difference between the hot and cold sides or faces of the panel. TheK factor varies with the average or mean temperature between the hot andcold faces of the material. The present panels are highly insulatingsince they have a K factor of less than 1.5 determined for an average ormean temperature range of 1000 degrees F. to 1750 degrees F. This, ofcourse, means that less than 1.5 B.t.u.s are lost by conduction through1 sq. ft. of a 1" thick panel in one hour for each degree F. differencebetween the hot and cold faces of the panel. The relatively low K factorindicates that the panels are highly insulating and particularly adaptedfor use in a hot top casing without a ceramic lining or directly in aningot mold.

The panel unit 10 is preferably formed by a vacuum or pressure wetmolding operation during which the flexible wire netting is immersed inthe aqueous slurry therein and in which the panels 10a, 10b are formedin a sideby-side open, unfolded position, as shown in FIG. 3, and in amanner to be hereinafter more fully described.

I The panel insert unit is adapted to be folded from its unfoldedposition shown in FIG. 3 to a position in which the adjacent side andcorner panels 10a, 10b are angnlarly related to form a tubular containerfor insertion into the opening 13 of the metal casing 11 by grasping theadjacent panels 10a, 10b and bending and stretching the flexible netting40 at and along the frangible portions 22 between the panels to an anglenecessary to bring the adjacent side edge surfaces 30, 31 of the panelsinto engagement with one another. During the folding movement of theadjacent panels 10a, 10b, the frangible portion 22 therebetween willbreak to allow the flexible screen 40 to bend so that the adjacent sideedge surfaces 30, 31 of the panels 10a, 10b properly mate to form thetubular container. The flexible netting holds the panels together afterthe frangible portions 22 are broken. The preformed insert unit 10, whenfolded to form the inner hot top lining, then is inserted into theopening 13 in the top of the metal casing. The bottom ring 16 and thewiper strip 18 are then secured in place and the hot top A is positionedin the opening at the upper end of the mold. The molten metal to formthe ingot is then poured through the hollow opening 13 in the hot top Aand the hot top is filled to the level desired. The panel insert unit 10makes a highly insulating container and provides that some of the moltenmetal in the hot top A will feed by gravity to the ingot in the mold tocompensate for shrinkage of the metal during solidification.

It has been found that by providing the frangible portions 22 forintegrally connecting the adjacent panels 10a, 10b, a strong flatconstruction is achieved which may be readily shipped withoutsignificant breakage, and yet when the adjacent panels are folded theyform a tubular container backed up by a hot top casing or mold wall. Byembedding the flexible wire netting 40 in the insert unit 10 closelyadjacent the bottom of the grooves, but between the bottom of thegrooves and the back faces 24 of the panels, the adjacent panels can befolded such that their adjacent joint surfaces mate along their entirelength. By providing reasonably tight joints between the adjacentpanels, metal leakage through the joints and behind the panels isminimized. Additionally, it has been found by substantially embeddingthe flexible wire netting between the back faces of the panel and thebottoms of the grooves that the panels, being reinforced by wirenetting, can withstand rough handling, and the inserts will holdtogether and be usable even if the panels are cracked during shipment,storage, and handling.

It should be noted that since the central opening 13 of casing 11 istapered, the panel insert unit 10, is designed so that when folded, itforms a generally trapezoidal tubular container. The insert unit 10,when in its fiat unfolded condition as illustrated in FIG. 3, issegmented and somewhat curved, and with the panels 10a being of atrapezoidal shape and panels 10b being rectangularly shaped. If thecentral opening of the casing is not tapered but is formed by parallelsides, then the insert unit in its fiat condition would be in the formof a rectangle and, when folded, would form a generally cylindricaltubular container.

FIG. shows another way in which the panel insert unit can be employed toform a hot top. The panel insert unit -10 is there shown as beinginserted down into and attached directly to the open upper end of aningot mold 50. The ingot mold 50, as shown in FIG. 5, is of theconventionally known, big-end-down type of ingot mold having adownwardly tapered central opening 52. A bigend-down type of ingot moldis one in which the central opening 52 is tapered so as to be larger atthe bottom than at the top thereof. It will, of course, be understoodthat the provisions of the present invention are also applicable to thebig-end-up type of mold and to molds having different contours.

The panel insert unit 10, when folded to form a tubular container orform whose sides are complementary to the sides of the opening 52, isadapted to be inserted into the opening of the mold 50 and attached toor held against the interior sides defining the opening 52 by anysuitable or conventional means to form a hot top, After the insert unit10 is in place, molten metal to form the ingot can then be pouredthrough the tubular container to the level desired to provide that someof the molten metal at the upper end of the ingot in the mold will feeddownward to compensate for shrinkage of the metal in the solidifyingingot.

The present invention provides a novel and economical method for makingthe panel insert unit 10. The method, in general, includes a one-stepmolding operation in which the panels 10a, 10b and the frangiblesections 22 are shaped as an integral unit and the flexible wire screenis embedded within the refractory material. The various steps incarrying out the method of the present invention will be described withreference to the description of an apparatus 55, schematically shown inFIGS. 6 and 7, for carrying out the method.

The apparatus 55 for carrying out the method of the present inventioncomprises a vacuum box 60 which is an open top box of the desired shapeand which has a horizontally disposed vacuum screen 61 backed up by astrong grid 61a extending thereacross at its upper end. The box 60 isprovided with an upwardly facing peripherally extending supporting ledge62 on which the vacuum screen 61 and grid 61a is supported. The vacuumscreen 61 defines with the sides and bottom of the box 60 a vacuumchamber 63 located beneath the vacuum screen 61. The vacuum chamber 63is adapted to be connected with a suitable vacuum source to provide orcreate a vacuum in the chamber 63 and the presence of the vacuum in thechamber 63 is designated generally by the arrow 64.

The contoured molding frame 70 comprises an outer frame part 71 shapedso as to provide the outer peripheral configuration of the panel insertunit 10 when in its flat position, as shown in FIG. 3. A plurality ofspaced bar members 72 are suitably secured to and extend transverselybetween the upper and lower generally longitudinal extending portions ofthe outer frame part 71, as viewed in FIG. 7. The bars 72 are employedto form the grooves 32 in the panel unit 10 and are spaced and disposedrelative to each other and the outer frame 71 so as to define with theouter frame 71 the configuration of the respective panels 10a, 10b to bemolded.

As best shown in FIG. 7, the bars are V-shaped to form the V-shapedgrooves 32 in the panel unit 10 and the inner vertically extending sides75 of the outer frame part 71 are suitably contoured or tapered toprovide the free side edge surfaces 30 and 31 of the two endmost panels.The top and bottom end surfaces at each panel have tapered surfacesformed by corresponding surfaces of frame 71. The outer frame part 71has a planar bottom surface 76 which is placed directly onto the vacuumscreen 61 and the bars 72 have their lowermost portions 78 located orspaced above the plane of the bottom surface 76 of the outer frame part71, and thus located above the vacuum screen 61, and for reasons to behereinafter more fully described.

In carrying out the steps of the method, the flexible wire netting 40 isplaced directly on the vacuum screen 61 and then a contoured moldingframe 70 movable relative to the box 60 is placed or positioned on topof the vacuum screen 61.

After the contoured molding frame 70 has been placed onto the vacuumscreen 61 to form a mold, this mold is filled with slurry of a suitablecomposition, such as the composition disclosed in the aforementionedpatent application, Ser. No. 401,944. The slurry covers the vacuumscreen 61 and surrounds and flows underneath the bar members 72 toprovide the frangible portions 22 and surrounds the wire netting tosubstantially embed the latter within the slurry. With the creation ofthe vacuum 64 the slurry is partially dewatered to leave a wet mat andthen the contoured molding frame 70 is moved upwardly relative to thevacuum box 60 to remove the same from the wet mat which willsubsequently become the panel insert unit 10.

By using the bar members 72 whose bottommost portions are spacedupwardly from the vacuum screen 61 so that the slurry flows beneath thebar members, accurate spacing between the adjacent joint surfaces 30, 31of the adjacent panels is achieved, which, in turn, enables miteredjoints to be effected when the panel insert unit is folded to form atubular container and a workable fit of the insert into the hot topcasing, or ingot mold. Moreover, it has been found that the employmentof this molding method enables the units to be more rapidly produced dueto the minimizing of air leakage through the slurry around the bottomand sides of the bar members and, thus, helps to prevent loss of vacuumaround the panel perimeters and enables the units 10 to be produced atrelatively low cost. Additionally, by substantially embedding theflexible screen within the refractory panel insert, loosening of thepanels from the screen and breakage of the panels is minimized oreliminated.

From the foregoing, it should be apparent that the objects hereinbeforeenumerated and others have been accomplished-and that a new and improvedhot top structure and method of making :the same have been provided.Although the .novel hot top structure and method of making the same ofthe present invention have been illus trated and described herein to adetailed extent, it will, of course, be understood that the invention isnot to be regarded as being limited correspondingly in scope and thatother changes and modifications can be made therein without departingfrom the spirit of the present invention.

Having described our invention, we claim:

1. A method of making a hot top structure which comprises a refractorypanel insert unit having front and back faces and a plurality of spacedgrooves extending thereacross whose bottoms are spaced from the backface of the panel insert unit to define a plurality of integrallyconnected refractory panels disposed in a side-by-side relationship andflexible hinge means imbedded within said refractory insert unit betweenthe bottom of the grooves and the back face of the insert unit tohingedly interconnect the adjacent panels, and which comprises the stepsof placing the flexible hinge means on a generally horizontally disposedporous base, placing a contoured mold of a shape to provide the desiredouter configuration of said one-piece refractory insert unit and whichhas a plurality of spaced bars whose bottommost portions are spacedupwardly from the plane of the bottommost surfaces of the remainder ofthe contoured mold onto said porous base to form a mold with thebottommost portions of said bars being spaced upwardly from said porousbase, pouring a refractory slurry into said mold with the slurry flowingaround said flexible hinge means and underneath said bars, dewateringsaid slurry, by applying a pressure differential to the top and bottomof the slurry, removing said contoured mold after said slurry has beensubstantially dewatered to form said one-piece refractory insert unithaving a flexible means imbedded therein, and completing the drying ofthe material composition of said refractory insert unit in an ovenmeans.

2. A method of forming a highly refractory insulating unit comprised ofa plurality of panels inter-connected by flexible material for relativeangular movement from an open flat position to a closed positiondefining a closed tubular structure comprising the steps of simul:taneously molding the adjacent panels in a mold ,cavity and formingintegral portions interconnectingadjacent panels adjacent one side ofthe unit with the flexible ma,- terial for hingedly connecting the sameimbedded in.the inter-connecting portions and the panels by flowingslurry of refractory material into a mold cavity having laterally spacedbars extending inwardly from one side thereof to separate one part ofthe mold cavity into mold spaces corresponding to the panels with theslurry beingof greater depth than the height of the bars to provide'atoneside of said panels a slurry receiving .space, filling the space sothat the slurry extends through said spaces coextensively with theunitby flowing slurry into said spaces and around said flexible materialdisposed in. said spaces to provide said interconnecting portions inwhich said flexible material is imbedded, dewatering the slurry todeposit the refractory material in the slurry in the mold by applying apressure differential to the topand bottom of the slurry, the flexiblematerial being. surrounded by slurry during dewatering so that it doesnot project outwardly of the deposited slurry when dewatering iscompleted, and removing the unit from the mold cavity and drying thesame at an elevated temperature,

3. A method as defined in claim-2 wherein the dewatering isaccomplishedby drawing water through holes in the bottom of the mold byusing a pressure below atmospheric and maintaining said co-extensiveportion during the dewatering operation to provide an air seal forpreventing the drawing of air along the sides of said bars.

References Cited UNITED STATES PATENTS 1,276,624 8/1918 Cummings 264-271X 2,054,499 9/ 1936 Florman.

2,361,386 10/1944 Eayrs 249197 X 2,850,786 9/1958 Dubbs 264 1013,216,689 11/1965 Carpenter 249-201 1. SPENCER OVERHOLSER, PrimaryExaminer R. D. BALDWIN, Assistant Examiner U.S. Cl. X.R.

